The goal of the proposed research is to investigate the role of CXCL12-driven nuclear LASP1 in modulation of epigenetic events in breast cancer. LASP-1 mediates cell migration, proliferation and survival in several breast cancer cell lines. Silencing of LASP-1 inhibits proliferation and migration by 45%. Previously, LASP-1 was demonstrated to directly interact with CXC chemokine receptors, CXCR1, CXCR2, CXCR3 and CXCR4 that play a key role in the tumor microenvironment facilitating breast cancer progression and metastasis. In particular, LASP-1 augmented CXCR2-mediated cell migration. Epigenetic alterations in breast cancer cells convert them into aggressive and metastatic phenotype. In this study, through proteomics, UHRF1 was discovered as a novel LASP-1 associating protein. Subsequently, DNMT1, G9a and Snail1 were also observed to associate with LASP-1. In particular, Snail1 was found to directly bind to LASP-1. The biological implication of this direct interaction is unclear. First, I propose to map the interaction sites between LASP-1 and Snail1 by mutational and biochemical approaches. I further propose to study the LASP1-Snail1 complex for its ability to modulate the E-cadherin promoter. Additionally, as Snail1 directly binds to lysine demethyalse1 (LSD1), LSD1 will be analyzed whether it associates with LASP1-Snail1 complex by biochemical studies. Functionally, I propose to perform a chromatin immunoprecipitation (ChIP) analysis for LASP-1, LSD1, and K4/9 methylation of histone H3 to see if LASP-1/LSD1 co-localize to regions with demethylated histones upon stimulation with CXCL12. Alternatively, recombinant LASP-1 will be mixed with purified LSD-1 and see if LASP-1 enhances in vitro demethylation activity on labeled histone H3 or nucleosome substrates. Additionally, non-silenced and LASP1-knock down basal- like breast cancer cells will be tested for their ability to facilitate bone resorption in a dentine disk assay. LASP1-Snail1 axis would become a novel drug target for small molecule inhibitors with the aim of prolonging the survival rate especially in triple-negative breast cancer patients. Novel inhibitors might be even more useful in cases of breast cancer that are resistant to current chemotherapeutic agents.
One out of every eight women will develop breast cancer in her lifetime and metastatic breast cancer is one of the leading causes of cancer deaths in women. Epigenetic events in the primary tumor are linked to invasion and metastasis in breast cancer. CXCL12-driven nuclear LASP-1 was discovered to associate with epigenetic proteins UHRF1, DNMT1, G9a and Snail1 that may play a critical role in shaping the epigenome that turns on or off the key molecular events leading to aggressive breast cancer and metastasis and eventual mortality.
| Butt, Elke; Raman, Dayanidhi (2018) New Frontiers for the Cytoskeletal Protein LASP1. Front Oncol 8:391 |
